Pattern Division Multiple Access System Research Articles

Research on improved multiple users detection algorithm in pattern division multiple access system

Receiver detection algorithm has always been a research hotspot in communication system and the key point to determine the performance of 5G system. Both industry and academia have been committed to finding detection algorithms with lower complexity and higher detection performance. This paper will study how to solve the problems of low detection performance and high complexity of classical algorithms. Taking Pattern Division Multiple Access (PDMA) as an example, this paper improves the existing receiver detection algorithms such as Minimum Mean Square Error-Serial Interference Cancellation (MMSE-SIC), Message Passing Algorithm (MPA) and Expectation Propagation Algorithm (EPA), and puts forward corresponding improved algorithms with specific formulas, i.e. Enhanced-MMSE-SIC, Turbo-like MPA (MPA-Turbo) and Turbo-like EPA with hybrid parallel interference cancellation (EPA-Turbo-PIC). Link-level simulation results and analysis show that the proposed improved algorithms have performance advantages over the corresponding traditional algorithms.

A novel power allocation strategy for cooperative PDMA systems

Cooperative communication technology is of great importance for increasing the user reachable rate, further improving throughput and reducing the outage probability of non-orthogonal multiple access (NOMA) systems. This paper mainly studies the power allocation optimization method based on amplify-and-forward (AF) pattern division multiple access (PDMA) to obtain the maximum achievable throughput. We formulate an optimization problem of user power allocation in a downlink PDMA system with cooperative relaying, the exact expressions of system throughput and user outage probability of the AF-PDMA system are derived, and a novel power allocation optimization method based on uniform distribution and restricted constraints is proposed. The effectiveness of the restricted constraints and optimization method is verified by theoretical analysis and simulation. The studies we have performed showed that the proposed scheme with uniform distribution and restricted constraints can be significantly improved in terms of the system throughput in comparison to the case with a genetic algorithm (GA) and fixed power allocation scheme. Concerning the proposed method, the search space is reduced to 1/3 of the original feasible region, and the runtime of the algorithm accounts for only 20% of the GA runtime.

The Design of Receiver with Low Complexity for PDMA System

As one of promising non-orthogonal multiple access scheme, pattern division multiple access (PDMA) scheme is considered to be one competitive multiple access technology for the fifth generation (5G) communications. The detection algorithm is the key technology to improve the system performance. Due to the PDMA patterns sparse nature, belief propagation (BP) become one effective receiver algorithm to achieve close to maximum likelihood (ML) detection performance with lower complexity. However, the complexity order is still exponential with the row weight of the PDMA pattern and the modulation index. A novel receiver based on expectation propagation (EP) algorithm is proposed in this paper to reduce the complexity order from exponential to linear. This paper makes a comparison on the two algorithms above in terms of system performance and complexity. Link-level simulation results show that the proposed EP receiver achieves nearly the same performance as the BP receiver with orders less complexity.

Demonstration of Pattern Division Multiple Access With Message Passing Algorithm for Multi-Channel mmWave Uplinks via RoF Mobile Fronthaul

Orthogonal multiple access (OMA) such as orthogonal frequency division multiple access (OFDMA) has been the predominant access technology adopted by the current generation of mobile communication. Representing an evolutionary step in radio access networks, non-orthogonal multiple access (NOMA) is considered to be a promising technology to meet the goals of increased capacity, enhanced flexibility, and reduced latency. Pattern division multiple access (PDMA) is a NOMA scheme using resource-element mapping as the multiple-access signature in the symbol level. This article introduces PDMA in a millimeter-wave (mmWave) radio access system with systematic experimental demonstration. One key advantage of PDMA is that it can facilitate advanced parallel interference cancellation (PIC) in the decoding process. A message passing algorithm (MPA) is developed and implemented in this article to enhance the decoding performance of PDMA. A novel PDMA system integrated with MPA is experimentally demonstrated in a multi-user mmWave radio access system that uses radio-over-fiber (RoF) mobile fronthaul, achieving reduced sensitivity penalty and improved modulation spectral efficiency compared to conventional power-domain NOMA (PD-NOMA) with successive interference cancellation (SIC). Experimental results show that PDMA is capable of supporting disparate channel conditions, adapting to various patterns, and providing improved system flexibility.

Low Complexity Iterative Receiver With Lossless Information Transfer for Non-Binary LDPC Coded PDMA System

In this work, we first proposed a non-binary low-density parity-check (NB-LDPC) coded pattern division multiple access (PDMA) scheme with the order of the Galois field equal to the size of modulation alphabet which can avoid the symbol-to-bit or bit-to-symbol probability conversion between the detector and decoder as in binary coded system. Specifically, we considered a 4-ary LDPC over Galois field (GF(4)-LDPC) coded PDMA system with quadrature phase shift keying (QPSK) modulation. At the receiver side, Gaussian approximation based message passing (GAMP) detection algorithm instead of standard message passing (SMP) is employed to achieve a tradeoff between the computational complexity and the detection performance. When iterative detection and decoding (IDD) algorithm is used, the symbol-wise extrinsic information of the detector and GF(4)-LDPC decoder can be exchanged without information loss. At last, we proposed a symbol-wise EXIT (S-EXIT) based iterative optimization algorithm to improve the system performance. Both the S-EXIT chart based analysis and numerical simulation results show the validity of the proposed scheme above.

Optimisation of convergence‐aware coded PDMA for 5G wireless systems

Orthogonal frequency division multiplexing-based pattern division multiple access (PDMA) is considered as a promising multiple access scheme for future wireless communication systems due to its high spectral efficiency and powerful ability to support massive users. In this study, it is shown that two pattern matrices with unequal diversity gain in the PDMA system have better convergence performance compared with the signature matrices in a traditional low-density signature multiple access system by simulations and extrinsic information transfer (EXIT) chart analysis. For a low-density parity check (LDPC)-coded PDMA system, the EXIT characteristics between the front-end multiple-user detector (MUD) and the LDPC decoder may be mismatch, which usually leads to degraded performance when an iterative detection and decoding algorithm is used. To overcome this problem, a two-stage iterative optimisation algorithm, which is easy to implement is proposed to find an optimal (near optimal) degree distribution pair for the LDPC code. Both EXIT chart analysis and simulation results demonstrate that the proposed algorithm exhibits further performance gain compared with regular (3,6) LDPC-coded systems under both an additive white Gaussian noise channel and a Rayleigh fading channel.

Pattern Division Multiple Access: A New Multiple Access Technology for 5G

The anticipated 1000-fold increase in mobile data traffic over the next decade and the explosion of new services and applications pose great challenges for the current orthogonal multiple access (OMA)-based 4G systems. A promising solution to address these challenges is to shift from the currently predominant OMA to non-orthogonal multiple access (NOMA). This article first introduces the principle of the complexity-constrained capacity-achieving NOMA design. Then a non-orthogonal pattern division multiple access (PDMA) scheme is proposed to meet the exponentially growing demand of mobile users for computing and information application services. The key feature of the PDMA scheme is a joint design of transmitter and receiver, which allows low-complexity successive interference cancellation (SIC)-based multi-user detection with substantially improved performance over conventional OMA schemes. More specifically, the patterns of multiple users are judiciously designed so that the data symbols of different users are of appropriate diversity disparity at the symbol level and power disparity at the resource element level. The appropriate disparity in diversity and power can be effectively exploited by the low-complexity SICbased detector to realize the near-perfect cancellation of multi-user interference. Moreover, the PDMA system parameters can be flexibly adjusted to provide different levels of overload, rendering it suitable to meet the diverse traffic requirements in future 5G systems. Link-level simulations illustrate that PDMA is capable of accommodating a 300 percent overload, while it still enjoys transmission reliability close to conventional OMA schemes. The results demonstrated in this article indicate that PDMA can be a promising multiple access technology with low signaling overhead, low latency, and massive connectivity support for 5G.

RIePDMA and BP-IDD-IC detection

Pattern division multiple access (PDMA) is a non-orthogonal multiple access (NOMA) scheme which is proposed to meet the demand of massive connection in the future 5G communications. In this paper, we build a random interleaver (RI) enhanced PDMA (RIePDMA) system by bringing the random interleaver into a PDMA system to further improve the overload of PDMA. Furthermore, we analyze several integrated detection and decoding algorithms with interference cancellation (IC) and propose the iterative detection and decoding based on belief propagation and interference cancellation (BP-IDD-IC). Simulation results show that the proposed RIePDMA system can achieve better block error rate (BLER) performance without increasing the complexity of the receiver. Compared with several other integrated detection and decoding algorithms, the proposed BP-IDD-IC algorithm can get better BLER performance with an acceptable complexity.